Light-Emitting Diode Display Device

This application claims priority for the TW patent application No. 113122657 filed on 19 Jun. 2024, the content of which is incorporated by reference in its entirely.

The invention relates to a display device, specifically a light-emitting diode (LED) display device.

Backlit liquid crystal (LC), semiconductor light-emitting diode (LED), and organic light-emitting diode (OLED) devices have been widely used in modern flat-panel displays, such as computer monitors, smartphone screens, and automotive displays. With the growing demand for more advanced visual devices in fields like virtual reality (VR), augmented reality (AR), and mixed reality (MR), there is increasing consideration of using micro light-emitting diode (micro-LED) and micro-OLED displays to meet the requirements for high resolution and high-density display manufacturing.

Pixels are the fundamental elements that make up images on a screen. In hardware, each pixel can be individually controlled to display text, graphics, images, or dynamic video. To manage power constraints and the required photon output, scanning technology addresses multiple rows of pixels simultaneously, sequentially lighting different image sections. The scanning rate and the number of frames per second (typically between 30 and 240 Hz) determine the overall frame rate. At a given frame rate, the number of pixel rows scanned at once affects the relative brightness of the display. Additionally, the duration of pixel activation under set electrical conditions ensures adequate brightness, which is a standard specification in display technology.

Different types of flat-panel displays are composed of various structural components. In general, flat-panel displays consist of three main types of components:

Both ends of the pixelated elements can be activated throughout the frame using a scanning method on the photonic section of the front plane. The electrodes can be configured as common anode (CA) or common cathode (CC) pixelated light-emitting components, enabling the display of images on a flat-panel display.

Conductive metals lack optical transparency and are typically used as electrodes in pixel array displays. The areas of these metal electrodes that do not cover the pixel illumination areas play a crucial role in determining the optical aperture ratio of the pixels, directly affecting the light emission efficiency and brightness produced by the pixels. Ideally, the layout of electrodes should minimize interference with pixel illumination. However, this creates a significant resistance between the pixel nodes and the voltage source terminals, increasing the impact of current resistance (IR) voltage drop. This behavior can negatively affect the uniformity of pixel performance across the entire array.

As displays move toward higher resolution and denser pixel layouts, requiring smaller light-emitting element sizes, the trade-off between the final aperture ratio and conductance of the common electrode becomes more complex. Under these conditions, optimizing electrode materials and structures becomes crucial.

Solving the challenge of IR voltage drop and its impact on uneven pixel luminescence and thermal energy waste depends in part on the program control of the line pixel activation algorithm and operational processing according to specific conditions. A comprehensive solution to the IR-drop problem of LED and OLED displays has yet to be generally established.

Therefore, this invention addresses the issues above by proposing a light-emitting diode display device to solve the problems present in conventional technologies.

This invention provides a light-emitting diode display device that reduces the impact of the current resistance (IR) drop in the common electrode layer and increases the pixel aperture ratio. As a result, the uniformity of pixel light emission is improved, achieving excellent pixel emission performance and efficiency. Additionally, by consuming less power to thermal energy, the display device can exhibit stable performance and have a longer lifespan.

In one embodiment of the present invention, a light-emitting diode (LED) display device includes a control circuit layer, multiple electrodes, multiple LEDs, and a common electrode layer. The control circuit layer is coupled to multiple scanning lines and data lines, which substantially intersect perpendicularly. The electrodes are placed on the control circuit layer and coupled to it, with the electrodes being isolated from each other. The LEDs are arranged in an array, each with two terminal electrodes. One terminal electrode of each LED is coupled to a corresponding electrode on the control circuit layer, and the other terminal electrode of the LED is connected to the common electrode layer. The common electrode layer consists of multiple equivalent one-dimensional electrode strips. At least one end of each equivalent one-dimensional electrode strip is coupled to a supply voltage, and the strips are respectively positioned along multiple columns of the LED array, coupled to the multiple columns of the LED array, and substantially intersected perpendicularly with the scanning lines.

In one embodiment of the present invention, the common electrode layer includes multiple groups of one-dimensional electrode segments coupled to the equivalent one-dimensional electrode strips, with the groups arranged in parallel. Each group of one-dimensional electrode segments contains multiple one-dimensional electrode segments coupled to the equivalent one-dimensional electrode strips and arranged alternately with the equivalent one-dimensional electrode strips, positioned substantially perpendicularly to them. For visible applications, the width of each equivalent one-dimensional electrode strip is greater than that of each one-dimensional electrode segment.

In one embodiment of the present invention, the LED display device includes a first-driver integrated circuit and a second-driver integrated circuit. The first driver-integrated circuit is coupled to the scanning lines, and the second to the data lines.

In one embodiment of the present invention, the control circuit layer includes multiple control circuits arranged in an array. The multiple columns of control circuits are coupled to the data lines, and the multiple rows of control circuits are coupled to the scanning lines. The electrodes are placed on the control circuits and are respectively coupled to them.

In one embodiment of the present invention, the equivalent one-dimensional electrode strips are made of conductive material.

In one embodiment of the present invention, the light-emitting diodes are semiconductor or organic light-emitting diodes.

In one embodiment of the present invention, each light-emitting diode is a monochrome or multi-color diode.

In one embodiment of the present invention, individual electrodes serve as cathodes, while the common electrode layer serves as the anode.

In one embodiment of the present invention, individual electrodes serve as anodes, while the common electrode layer is the cathode.

In one embodiment of the present invention, one end or both ends of each equivalent one-dimensional electrode strip are coupled to a supply voltage.

Based on the above, the LED display device forms equivalent one-dimensional electrode strips that intersect the scanning lines perpendicularly, reducing the impact of current resistance (IR) voltage drop in the common electrode layer. This embodiment simultaneously increases the pixel aperture ratio, achieving outstanding pixel luminous efficiency and uniformity while dissipating less thermal energy and enhancing the stability and lifespan of the display device.

Below, the embodiments are described in detail in cooperation with the drawings to make the invention's technical contents, characteristics, and accomplishments easily understood.

The embodiments of the present invention will be further explained below concerning relevant figures. The same reference numbers are used in the drawings and description wherever possible to refer to the same or similar components. In the drawings, shapes and thicknesses may be exaggerated for simplicity and ease of notation. It should be understood that elements not explicitly shown in the drawings or described in the specification are in forms known to those of ordinary skill in the art. Those skilled in the art can make various changes and modifications based on the contents of the present invention.

When a component is referred to as “on,” it can refer to that component being directly on another element, or it can also mean that other components are present between the two. Conversely, when a component is referred to as “directly on” another component, there cannot be any other components between the two. As this document uses, “and/or” encompasses any combination of one or more related items.

The description of “one embodiment” or “an embodiment” in the following text refers to a specific component, structure, or feature associated with at least one embodiment. Therefore, the text's multiple references to “one embodiment” or “an embodiment” do not refer to the same embodiment. Furthermore, the specific components, structures, and features in one or more embodiments may be combined appropriately.

The disclosure describes explicitly the following examples, which are only for illustrative purposes. For those familiar with this technology, various modifications and refinements can be made without departing from the spirit and scope of this disclosure. Therefore, the protection scope of this disclosure should be defined by the following claims. Throughout the specification and the claims, unless specified otherwise, the terms “a” and “the” include instances of “one or at least one” of the component or ingredient. Furthermore, as used in this disclosure, unless it is evident from the specific context that plural forms are excluded, singular articles also encompass plural components or ingredients. Additionally, when applying the descriptions herein and in the following claims, unless specified otherwise, the term “therein” may include “therein” and “thereon.” In terms of terminology used throughout the specification and claims, unless expressly noted, each term typically carries its ordinary meaning in the field, within the context of this disclosure, and in the particular context. We want to discuss specific terms used to describe this disclosure further below or elsewhere in this specification to provide practitioners with additional guidance regarding the description of this disclosure. Any examples provided throughout this specification, including the use of any terms discussed here, are illustrative and do not limit the scope and meaning of this disclosure or any illustrative terms. Similarly, this disclosure is not limited to the various embodiments presented in this specification.

It can be understood that the terms used herein, such as ‘comprising,’ ‘including,’ ‘having,’ ‘containing,’ ‘involving,’ etc., are open-ended, meaning they include but are not limited to the listed items. Furthermore, any embodiment of the present invention or the scope of the patent application can achieve some of the purposes, advantages, or features disclosed in this invention. Additionally, the abstract and title are intended solely to assist in searching patent documents and are not meant to limit the scope of the invention claimed.

Furthermore, the term ‘electrical coupling’ or ‘electrical connection’ herein includes any direct or indirect electrical connection means. For example, suppose the text describes a first device electrically coupled to a second device. In that case, the first device can be directly connected to the second device or indirectly connected to the second device through other devices or connection means. Additionally, when describing the transmission or provision of electrical signals, those skilled in the art should understand that the transmission of electrical signals may be accompanied by attenuation or other non-ideal variations. However, if the source and receiving end of the electrical signal transmission or provision are not explicitly stated, they should be regarded as effectively the same signal. For instance, if an electrical signal S is transmitted (or provided) from endpoint A of an electronic circuit to endpoint B of the electronic circuit, there may be a voltage drop across the source and drain of a transistor switch and/or possible stray capacitance; however, if the design does not intentionally use the attenuation or other non-ideal variations generated during transmission (or provision) to achieve specific technical effects, the electrical signal S at endpoints A and B of the electronic circuit should be considered effectively the same signal.

Unless otherwise specified, specific conditional phrases or terms such as ‘can,’ ‘could,’ ‘might,’ or ‘may’ typically attempt to express features that are present in this embodiment but can also be interpreted as characteristics, components, or steps that may not be necessary. In other embodiments, these features, components, or steps may be unnecessary.

The terms ‘substantially,’ ‘around,’ ‘about,’ or ‘approximately’ used herein generally mean within 20% of a given value or range, preferably within 10%. Furthermore, the quantities provided here may be approximations, which means that in the absence of specific statements, they can be indicated by the terms ‘around,’ ‘about,’ or ‘approximately.’ When a quantity, concentration, or other numerical value or parameter has a specified range, preferred range, or ideal values listed, it should be understood as specifically disclosing all ranges constituted by any pairs of lower and upper limits or ideal values, regardless of whether those ranges are separately disclosed. For example, suppose a disclosed range states that a length is from X centimeters to Y centimeters. In that case, it should be considered as revealing a length of H centimeters, where H can be any actual number between X and Y.

The term ‘effective one-dimensional electrode strip’ herein refers to a one-dimensional electrode strip with varying widths along the main line direction. It may possess structural variations in the transverse local shape, such as a serrated pattern. The degree of variation in these effective widths is less than 10% of the length of the one-dimensional electrode strip.

The following describes the invention's light-emitting diode display device, which forms equivalent one-dimensional electrode strips that intersect perpendicularly with the scan lines. This configuration reduces the impact of current resistance (IR) voltage drop in the common electrode layer and increases the pixel aperture ratio. As a result, it achieves excellent pixel luminous efficiency and uniformity in emission while operating under conditions that generate lower thermal power, leading to stable performance of the light-emitting device and a longer component lifespan.

is a schematic diagram of a light-emitting diode in an embodiment of the present invention. Referring to, a typical light-emitting diodeincludes a first semiconductor layer, a quantum well layer, and a second semiconductor layer, stacked in that order. Electrodesandare respectively placed on the first semiconductor layerand the second semiconductor layer. The first semiconductor layerand the second semiconductor layerhave a first conductivity type and its opposite second conductivity type, respectively. When the first conductivity type is N-type, the second conductivity type is P-type. Conversely, when the first conductivity type is P-type, the second conductivity type is N-type.

is a schematic diagram showing a light-emitting diode of an embodiment of the present invention positioned on a control circuit layer. Referring to, the first semiconductor layeris placed on a control circuit layerthrough electrodeto facilitate pixel operation control. Electrodepartially covers the second semiconductor layerwithin the pixel.is a schematic diagram of a light-emitting diode in another embodiment of the present invention, situated on a control circuit layer.depicts an electrodesimilar to that in, characterized by cutouts on its four sides, which are optional and unnecessary in some cases. This design allows electrodeto pass through the isolated pixel sidewalls, although this is not explicitly shown here. This configuration is particularly significant for stacking tricolor light-emitting diodes, aiding their integration with the control circuit layer, even though this is not illustrated in the figure. Such integration enhances the overall functionality and performance of the light-emitting diode array.

Various methods and techniques can be employed to create light-emitting diode (LED) pixel arrays and display panels. Control circuits connected to the scan, data, and clock lines can utilize complementary metal-oxide-semiconductor (CMOS) pixel driving circuits (PDC). This enables displaying images and videos in different scanning modes, including single-pixel, multi-pixel, and pixel line scan modes. In the well-known line scanning mode, the LED pixels are configured either as the common anode (CA) or a common cathode (CC). This allows the electrodes of each pixel to connect to their respective PDCs and compatible current regulation circuits within the (m×n) pixel array. This scheme provides high-quality image and video displays at standard resolutions, such as 640×360 for one-ninth HD (nHD), 1280×640 for HD, and 1920×1080 for full HD (FHD).

is a schematic diagram of a light-emitting diode display device with a common electrode layer. Referring to, electrodeinextends outward to form the common electrode layer, shown in. The common electrode layeris arranged in a two-dimensional grid pattern, forming multiple electrodeson the control circuit layer, which are connected to the (m×n) electrodesof the light-emitting diodes, thus creating the light-emitting diode display device illustrated in. Both m and n are positive integers greater than 1. In this example, both m and n are equal to 3.”

corresponds tobut features a non-limited size (m×n) light-emitting diode (LED) array and additionally includes an equivalent circuit diagram supplying a voltage VDD. Please refer to. The common electrode layercontains multiple horizontal and transverse parasitic resistors. The corresponding horizontal and transverse parasitic resistors in each LED unit arise from the limited conductivity of the wiring, the finite thickness of the wiring, and its effective width. The horizontal and transverse parasitic resistors are coupled and connected to a terminal that supplies the voltage VDD. The horizontal parasitic resistor in the i-th column and the j-th row is represented as Rh(i,j), the transverse parasitic resistor in the i-th column and the j-th row is represented as Rt(i,j), and the LED in the i-th column and the j-th row is represented as D(i,j), where both i and j are positive integers greater than 0. The control circuit layerincludes multiple control circuits and current sources, the first driving integrated circuit IC1 and the second driving integrated circuit IC2. The current source in the i-th column and the j-th row is represented as I(i,j), and the control circuit in the i-th column and the j-th row is represented as C(i,j). Each control circuit is coupled to a scan line SC and a data line DA; the scan line SC is coupled to the first driving integrated circuit IC1 and is used to transmit pulse width modulation voltage, while the data line DA is coupled to the second driving integrated circuit IC2. Each control circuit is coupled to a ground through its corresponding current source. In this embodiment, the common electrode layerserves as the anode of LED, electrodeserves as the cathode of LED, the first conductivity type of the first semiconductor layeris N-type, and the second conductivity type of the second semiconductor layeris P-type.

The compliance-regulated current source I(i,j) for each pixel may not be necessary for the light-emitting displays. However, such compliance, regulation, or reference current sources can effectively control high-quality flat-panel displays that require uniform pixel brightness behavior. It ensures consistent current flow through all pixels, producing uniform brightness during the same active period. This is especially true regardless of the voltage drop across the light-emitting diode during operation. Since the light-emitting elements in the same device generally have similar external quantum efficiency (EQE), a relatively good uniformity of light emission can be achieved. Otherwise, controlling or setting the voltage across the light-emitting device might take a lot of work.

In a simplified analysis, the parallel row or column traces intersecting at the pixel edges can be collectively referred to as a single row or column trace, with its effective width denoted as w. Therefore, the parasitic resistance value of the horizontal standard electrode layerfor each pixel can be calculated using the formula ρ·l/(w·t), where ρ represents the resistivity of the common electrode layer, l is approximately the pixel pitch, w is the effective width of the cross-section of the strip portion surrounding the pixel, and t is the thickness of the common electrode layer. Due to the symmetrical configuration of the mesh electrodes in both the horizontal and transverse directions, the value of the horizontal parasitic resistance can be considered approximately equal to that of the transverse parasitic resistance.

is another equivalent circuit diagram corresponding to, showing an array of (m×n) light-emitting elements and the supply voltage VDD.is similar to. Please refer to, and: the common electrode layerserves as the cathode of the light-emitting diode, and electrodeserves as the anode of the light-emitting diode. The first conductivity type of the first semiconductor layeris P-type, and the second conductivity type of the second semiconductor layeris N-type. Therefore, the current direction of the current source inis opposite to that in. Despite the polarity and current direction differences between the common-anode and common-cathode cases, their behavior, trends, and final effects remain consistent.

To improve the efficiency of standard LED displays, the supply voltage VDD is typically adjusted within the range of 3-5V, customized explicitly for red, green, and blue light-emitting diodes. This voltage can be fine-tuned to minimize power consumption, ensuring that the light-emitting diodes in the pixels operate within the saturation current region controlled by a compatible current source.

illustrates a schematic of a light-emitting diode display device with equivalent one-dimensional electrode strips parallel to the scan lines. The direction of the scan line is marked for reference. Please refer to;differ in the shape of the common electrode layer. The two-dimensional grid shape of the common electrode layerinis replaced by multiple equivalent one-dimensional electrode strips, forming the common electrode layerin, where the equivalent one-dimensional electrode stripsare parallel to the scan lines. Compared to, the area of the common electrode layerinis reduced by about half, which decreases the coverage of the illuminating region of the light-emitting diodes, allowing for a larger optical aperture. Therefore, when operating under the same bias conditions and without other influencing factors, pixels with equivalent one-dimensional electrode strips can achieve higher light-emitting efficiency than pixels with a two-dimensional grid-shaped common electrode layer.

corresponds tobut features a light-emitting diode array of unspecified size (m×n) and additionally includes the equivalent circuit diagram for the supply voltage VDD.omits the transverse parasitic resistance compared with. The other features remain the same as inand will not be repeated here. As shown inand, the horizontal parasitic resistance value of the common electrode layerfor each pixel is calculated using the formula ρ·l/(w·t), where ρ represents the resistivity of the common electrode layer, l is approximately the pixel pitch, w is the effective width of the cross-sectional strip surrounding the pixel, and t denotes the thickness of the common electrode layer.

is a counterpart to, presenting another equivalent circuit diagram of the (m×n) light-emitting element array with supply voltage VDD. Unlike,omits the transverse parasitic resistance; however, all other features are identical to those inand will not be repeated here.

As mentioned earlier, the current source I(i,j) values are uniformly set to a constant value to ensure consistent lighting conditions for the pixel LEDs, achieving a high degree of uniformity in image display. Systemically, the entire (m×n) display device can simultaneously activate multiple designated rows of LEDs within the scanning interval to achieve the desired image brightness.

The resistance values of all horizontal parasitic resistors are typically the same, ensured through standard design rules and manufacturing processes that maintain a constant resistance value for the horizontal parasitic resistors. These horizontal parasitic resistors create what is commonly called “IR voltage drop.” All selected active pixels are assumed to receive the same current to evaluate the IR voltage drop effect generated by the common electrode layer coupled to the supply voltage VDD. Considering symmetry and that both ends of a one-dimensional electrode line are connected to the supply voltage VDD, half of the pixels receive current from one side.

In an LED array with m columns and n rows, selecting the LED D(i,j) for scanning refers to choosing the diode in the i-th column and j-th row for activation. Here, it is assumed that i=m/2, positioning the selection in the central row. A constant compliance reference current Iref flows through the horizontal parasitic resistor Rh(m/2,j) to the anode or cathode of the light-emitting diode D(m/2,j), resulting in a voltage drop across both ends of the horizontal parasitic resistor equal to Rh×Iref, where Rh represents the resistance value of the horizontal parasitic resistor, and Iref represents the current flowing through each light-emitting diode D(i,j), which is the current of the current source I(i,j).

The current through the horizontal parasitic resistor Rh(m/2−1,j) is composed of the current Iref through the anode or cathode of the light-emitting diode D(m/2−1,j) and the current Iref through the horizontal parasitic resistor Rh(m/2,j). Similarly, the current through the horizontal parasitic resistor Rh(1,j) is composed of the current Iref through the anode or cathode of the light-emitting diode D(1,j) and the current flowing through the horizontal parasitic resistor Rh(2,j). Since the current through the horizontal parasitic resistor Rh(2,j) is equal to (m/2−1)×Iref, the voltage drop across both ends of the horizontal parasitic resistor Rh(1,j) is equal to (m/2)×Iref×Rh.

Therefore, in the case of scanning lines being parallel to an equivalent one-dimensional electrode strip, the maximum voltage difference between the supply voltage VDD and the anode or cathode of the light-emitting diode located in the middle of the pixel array, represented as V, is approximately as shown in formula (1).